Characterizing the spatial and temporal variation of malaria incidence in Bangladesh, 2007

Reid, Haque Ubydul, Roy Shyamal, Islam Nazrul, Clements

Description

Malaria remains a significant health problem in Bangladesh affecting 13 of 64 districts. The risk of malaria is variable across the endemic areas and throughout the year. A better understanding of the spatial and temporal patterns in malaria risk and the determinants driving the variation are crucial for the appropriate targeting of interventions under the National Malaria Control and Prevention Programme. Methods Numbers of Plasmodium falciparum and Plasmodium vivax malaria cases reported by month in 2007, across the 70 endemic thanas (sub-districts) in Bangladesh, were assembled from health centre surveillance reports. Bayesian Poisson regression models of incidence were constructed, with fixed effects for monthly rainfall, maximum temperature and elevation, and random effects for thanas , with a conditional autoregressive prior spatial structure. Results The annual incidence of reported cases was 34.0 and 9.6 cases/10,000 population for P. falciparum and P. vivax respectively and the population of the 70 malaria-endemic thanas was approximately 13.5 million in 2007. Incidence of reported cases for both types of malaria was highest in the mountainous south-east of the country (the Chittagong Hill Tracts). Models revealed statistically significant positive associations between the incidence of reported P. vivax and P. falciparum cases and rainfall and maximum temperature. Conclusions The risk of P. falciparum and P. vivax was spatially variable across the endemic thanas of Bangladesh and also highly seasonal, suggesting that interventions should be targeted and timed according to the risk profile of the endemic areas. Rainfall, temperature and elevation are major factors driving the spatiotemporal patterns of malaria in Bangladesh.

Sujets

• Malaria
• Bangladesh
• Espace
• Temporal
• Seasonality
• Bayesian
• Plasmodium falciparum
• Plasmodium vivax

Informations

• Publié par: biomed
• Publié le: 01 janvier 2012
• Nombre de lectures: 11
• Langue: English

Extrait

Reidet al. Malaria Journal2012,11:170 http://www.malariajournal.com/content/11/1/170

R E S E A R C H

Open Access

Characterizing the spatial and temporal variation of malaria incidence in Bangladesh, 2007 1 2 3 3 1* ˆ Heidi L Reid , Ubydul Haque , Shyamal Roy , Nazrul Islam and Archie CA Clements

Abstract Background:Malaria remains a significant health problem in Bangladesh affecting 13 of 64 districts. The risk of malaria is variable across the endemic areas and throughout the year. A better understanding of the spatial and temporal patterns in malaria risk and the determinants driving the variation are crucial for the appropriate targeting of interventions under the National Malaria Control and Prevention Programme. Methods:Numbers ofPlasmodium falciparumandPlasmodium vivaxmalaria cases reported by month in 2007, across the 70 endemicthanas(subdistricts) in Bangladesh, were assembled from health centre surveillance reports. Bayesian Poisson regression models of incidence were constructed, with fixed effects for monthly rainfall, maximum temperature and elevation, and random effects forthanas, with a conditional autoregressive prior spatial structure. Results:The annual incidence of reported cases was 34.0 and 9.6 cases/10,000 population forP. falciparumand P. vivaxrespectively and the population of the 70 malariaendemicthanaswas approximately 13.5 million in 2007. Incidence of reported cases for both types of malaria was highest in the mountainous southeast of the country (the Chittagong Hill Tracts). Models revealed statistically significant positive associations between the incidence of reportedP. vivaxandP. falciparumcases and rainfall and maximum temperature. Conclusions:The risk ofP. falciparumandP. vivaxwas spatially variable across the endemicthanasof Bangladesh and also highly seasonal, suggesting that interventions should be targeted and timed according to the risk profile of the endemic areas. Rainfall, temperature and elevation are major factors driving the spatiotemporal patterns of malaria in Bangladesh. Keywords:Malaria, Bangladesh, Spatial, Temporal, Seasonality, Bayesian,Plasmodium falciparum,Plasmodium vivax

Background Spatial and temporal variability in malaria transmission are known to be driven partly by ecological factors that affect the survival and population size of anopheline vectors. Temperature, humidity and water available for breeding habitats have been shown to be important primary eco logical factors [1]. Fluctuation in malaria risk has significant public health implications for ensuring adequate provision of antimalarials, the delivery of intermittent preventative therapy (IPT) and optimizing the timing and frequency of indoor residual spraying with insecticides and/or distribu tion of longlasting insecticidal nets (LLIN), and thus war rants investigation.

* Correspondence: [e-mail] ˆ Deceased 1 Infectious Disease Epidemiology Unit, Level 4 Public Health Building, School of Population Health, University of Queensland, Herston, QLD 4006, Australia Full list of author information is available at the end of the article

At a macroscale, attempts have been made to under stand the mechanisms driving malaria risk. The Mapping Malaria Risk in Africa (MARA) collaboration developed maps that describe the expected duration and timing of the transmission season by country based on climate suit ability models [2,3]. Insight into the underlying ecological mechanisms both inhibiting and propelling malaria trans mission has led to research into malaria early warning sys tems (MEWS) to be able to predict disease patterns based on known relationships between the disease and eco logical variables [411]. A host of issues, however, make characterizing the nat ural phenomena underlying spatial and temporal patterns in malaria risk difficult. Differences in ecological require ments between malaria vectors mean that particular envir onmental events, such as the rainy season, can lead to an increase in vector capacity for most vectors but an initial

© 2012 Reid et al.; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.